U.S. Pat. No. 4,417,754, Yamaji et al, discloses a separation preventive pipe joint comprising a holding member connectable to an annular outer flange formed at the end of a socket and surrounding the outer periphery of a spigot outside the socket, the holding member being annular or being adapted to form an annular shape, the holding member being provided on its inner periphery with a tapered surface increasing in diameter toward the socket; a stopper in the form of a ring divided at one portion and provided with an outer peripheral tapered surface increasing in diameter toward the socket and with engaging edges in circumferential rows on its inner periphery, the stopper being interposed between the tapered surface of the holding member and the spigot outer periphery; and tap bolts extending through the holding member at suitable portions along its circumference for pressing the stopper from outside against the spigot outer periphery.
According to this arrangement, when a separating force acts on the spigot, the engaging edges of the stopper ring engage in the spigot outer periphery to a greater degree by the wedging engagement of the stopper outer periphery with the tap bolts and/or the tapered inner periphery of the holding member, consequently producing an increasing separation preventive force. However, the prior art pipe joint has the following disadvantages.
(1) Since the stopper ring engages non-elastically with the tap bolts and the spigot outer periphery, the ring cannot fully follow or cope with the oscillation of the spigot relative to the socket, the oscillation being caused by internal fluid pressure variations (pulsating fluid flow) or other external influences. This results in loosening of the related parts after long use, ultimately leading to complete loss of separation prevention.
(2) The non-elastic engagement of the stopper ring allows a great separating force to be transmitted directly to the tap bolts and the holding member, possibly leading to breakage of the bolts and/or the holding member.